NMR of Nb-93 perturbed by quadrupole interaction in quasi-one-dimensional BaNbS3+d

Field-swept NMR spectra of Nb-93 are examined for a sample of BaNbS2.96 whi ch has a semiconductive temperature dependence of the resistivity at low te mperature, and a sample of BaNbS3.03 which has a metallic temperature depen dence at low temperature. Both spectra are so-called NMR powder patterns pe rturbed by a quadrupole interaction with a quadrupole frequency v(Q) = 3e(2 )qQ/2I(2I - 1)h of 2.5 [MHz]. No appreciable difference in the spectra has been observed between the two samples, suggesting that the amplitude of the conduction electron density is too small to perturb the electronic environ ments around the niobium atoms. The general behavior of the nuclear spin-la ttice relaxation of Nb-93 in both compounds is consistent with an interpret ation that the relaxation at: low temperature is dominated by a Korringa me chanism and at higher temperature by a quadrupole interaction.